This invention lies in the field of low power visible light source apparatus and, more particularly, apparatus for providing a source of visible light for curing photo-curable compositions such as are utilized in dental work.
In the field of dentistry there have been recent developments which have increased the need for an efficient apparatus for delivering light in the visible range, and particularly the range of about 400 to 500 nanometers, to activate the polymerization of certain kinds of photo-curable compositions to produce dental sealants, dental filling materials, dental adhesives and the like. In addition, other uses for photocurable compositions, particularly as adhesives, have been and are being developed. There has thus come into being a great need for a highly efficient and reliable light source apparatus which is flexible, can be easily hand held and manipulated, and which is safe for use.
In the past, ultraviolet radiation has been used extensively as one mechanism for activating photo-curable materials. For many applications, including the dental area, it has been found that visible light curable compositions are preferred. Visible light is more efficient in crossing the boundary between two dissimilar materials, and is passing through material which has already been cured. It is preferred in many dental applications because it can pass through tooth structure. Also, recent photo-curable compositions which have excellent properties as adhesives in industry in general have been found which require visible light for curing. Still further, the operator, e.g. the dentist, can see the visible light when it is directed at a small operating surface, and this gives a degree of operator feedback which is useful in many applications.
A number of problems exist in the design of a light apparatus for curing photo-curable compositions. First, for most all applications, including the dental one, it is necessary that the apparatus be safe for operator handling. This means that stray light emission must be either eliminated or reduced to safe levels, that the light must be concentrated at a specific small area, and that the light emitted at the small area be within biologically safe limits. Further, the apparatus must be easily manipulable, leading to the demand for a small handpiece, which handpiece is light in weight and does not heat up. For this reason, there should be means for producing that light at a location somewhat remote from the point of light application, and means for guiding the light from the location where it is generated to a specific small area where the operator can irradiate the compositions which are sensitive to and cured by the visible light. There are also substantial demands placed on the optical system, whereby there is provided light essentially limited to the desired bandpass range, e.g. 400 to 500 nm. Further, in most applications it is desirable to operate the light source in an on-off mode, and this imposes requirements on the power supply functional design and the lamp itself, so as to achieve a light source which maintains specified operating characteristics and achieves a satisfactory life time.